Technical Field
The present invention relates to an image forming apparatus, an image forming method, and a non-transitory recording medium storing an image forming program.
Background Art
In known image forming apparatuses referred to as multifunction peripherals (MFPs) integrating multiple functions such as a printer, a copier, a scanner, and a facsimile etc., an operation of charging surface potential of a photoconductor uniformly is included in an electrophotography process. A non-contact charging method that a charging roller that functions as a charging unit is located to hold slight gap with the surface of the photoconductor that functions as an image bearer and high voltage superimposing sine AC voltage on DC voltage is applied to the charging roller is known as one of charging methods. By contrast, a contact charging method that the charging roller is located to contact the photoconductor without a gap is also known. By adopting those methods, it is possible to discharge between the charging roller and the surface of the photoconductor and acquire uniform surface potential of the photoconductor. Generally, in these methods, it is considered that the surface voltage of the photoconductor is equal to DC component of the applied voltage, and it is possible to control the surface potential of the photoconductor by adjusting the DC voltage.
Here, it is required to charge the surface of the photoconductor uniformly at desired voltage to form a high-quality image. To cope with this issue, a technology that charges the surface of the photoconductor at desired voltage by keeping a peak value of the applied sine AC voltage equal to or more than a predetermined value is known.
However, if the peak value of sine AC voltage becomes too high, discharge is generated more than needs, and the photoconductor is degraded by oxide such as ozone and NOx generated by the discharge more than expected. To cope with this issue, a technology that can adjust charging bias at any time regardless of whether or not an image is formed is known.